Electrical apparatus



June 99 i942. J. W. ALLEN 2,285,397

ELECTRICAL APPARATUS Filed March l0, 1941 INVENTOR Patented June 9, 1942 ELECTRICAL APPARATUS Joseph W. Allen, East range, N. J., signor to Bendix Aviation Corporation, South Bend, Ind., a corporation oi' Delaware Application March 10, 1941, SerlalNo. 382,373 2 Claims. (Cl. 171-229) This invention relates to dynamo electric machines, and particularly to the regulation of the voltage across the output lines of a dynamo electric machine.

Direct current generators whose capacity is suillciently high to require neld current ilow in excess of a few amperes present a problem in voltage output regulation which is not satisfactorilyA met by use of vibrating regulators connected in the manner that has become standard in automotive vehicle installations which-until a very recent dutch-did not involve generator loads in excess of, say, fty amperes, or voltage outputs in excess of nfteen to thirty volts.

Recent developments in the automotive held,

particularly in the design of buses, aircraft and marine craft to transport heavier loads under power developed by internal combustion engines. have involved constantly increasing demands for generation of more electrical power by use of engine-driven generators of higher capacities than heretofore. The result has been to create a problem in satisfactory voltage regulation.

As a proposed solution of this problem it is an object of the present invention to provide a generator system in which the vibrating regulator operates upon the shunt ileld only indirectly, and in such manner that its contacts are outside the shunt ileld circuit and therefore do not have to carry the relatively heavy ileld current.

A further object is to provide, for generator voltage regulation, an automatically operated rheostat which varies the strength of the gener ator eld immediately upon the occurrence of a rise or fall in line voltage, and then holds the new setting steadily, the operation of the rheostat being under the control of a voltagerespon` sive vibratory regulator.

In the preferred embodiment shown in the accompanying drawing, the rheostat is operated byv an electric motor, the armature of whichis connected in series with the armature of the vibratory regulator, and in such manner that both said armatures are located in the .common central portion of a network of connections across the output terminals of the generator whose voltage is-to be regulated, wherefore current may flow through the windings of the motor amature in opposite direction, alternately. and thereby cut resistance in and out, alternately, in the rheostat section oi' the generator neld circuit. It is to be understood, however, that the maintenance of the electrical connections precisely as shown is not essential, the drawing being illustrative rath- Otherobjects include mechanical features of the rheostat, the rheostat drive, the driving motor, and the vibratory regulator, and will become apparent from inspection of the following speclncation when read with reference to the accompanying drawing wherein is illustrated the preferred embodiment of the invention. It is to be expressly understood, however. that the drawing is for the purpose of illustration only, and is not designed as a deilnition of the limits of the invention, reference being had to the appended claims for this purpose.

In the drawing,

Fig. l is a diagram of the electrical connections involved in the preferred embodiment of the invention, with certain of the actuating elements being shown in mechanical section; and

Fig. 2 is a view, in perspective of a portion of the box which houses the voltage regulating motor.

In Fig. l reference characters i and t designate the two sides of the circuit supplied by the generator 1, and numeral l designates the rotating contact arm of a rheostat forming part of the shunt field circuit of the generator, and therefore connected in series with the ileld windings Y l and the circuit-protecting relay il. The rheoer than deilnltive of the scope oi' the invention. 55

stat arm l is adapted to be rotated ilrst in one direction and then the other, ln response to the rotation of a reversing electric motor Il; the reversals of said motor being under the control oi an electromagnetic assembly 2l mounted on a suitable insulating panel (not shown) the armature M of the assembly having a contact il* adapted to engage a stationary contact It, and a second contact Mb adapted to engage a stationary contact mounted directly under the contact lll' on a strip Il secured to (but insulated from) the H-shaped iron plate `Il which tits between the parallel iron plates 2i and Il of the magnet assembly and is secured thereto by pins 2l, 2l. A third pin 2l is iournaled in the upper extensions of plate 22 and receives the ears 2l oi the armature il, wherefore the said armature il has pivotal suspension for oscillation between the contacts Il and Il. A coiled spring 3l holds the amature balanced mid-way between the contacts il and i1. and out oi' engagement therewith, so long as the voltage across lines I and that is, across the output terminals of the generatori-remains at the rated value; the tension of the spring being adjustable to assure such balancing oi' the armature il. and the adjusting means having certain novel features hereinafter described.

In order to make the armature |4 of the motor energizing magnet responsive to deviations from normal voltage, I place upon its core 38 a pair ofwindings 88 and 31, the former of which is connected (along with its resistor 88) directly across the lines 5 and 6. The winding I1 is also (along with its resistor 39) connected directly across the lines 8 and 8, but only by way of the normally open contacts I4, I8 to which leads 4|, 42, respectively, are connected. Because of this difference in hook-ups, it followsthat the magnetic (downward) pull upon armature |4 will be constant so long as the voltage across lines 8, 8 is constant; will decrease when the voltage across lines 8, 8 drops below normal, thus allowing spring 3l to swing the armature upward to engage contacts |4- with I8; and will thereupon tend to increase by reason of the direct connection thus established between outer winding 31 and the wire 42 leading to the negative side of the line. Whether this increase will be sufilcient to offset instantly the effect of spring 8| will depend upon how far below normal the voltage across the lines 5, 6 has dropped. In any event, the closure of contacts I4n and I6 will have brought about an energization ofthe armature windings of the motor I3 and a consequent rotation of the rheostat arm 8 in a clockwire direction; the circuit through the motor I3 being traceable from positive side 5 by way oi' wires 5|,

82 and 88, and back to the negative side by way of wires 84, 58, 4| and 42; the two last-named being connected by the engagement of contact I4* with contact I6. The resulting clockwise rotation of arm 8 operates to reducethe amount of resistance in the shunt field circuit of generator 1; hence said .field circuit is strengthened and the generator voltage restored toward normal. Restoratlon toward normal voltage will have a strengthening eilect on the magnetic circuitv of windings 88 and V81, andthe resulting increase in the downward pull on armature I4 should cause a reopening of the contacts |4'- and I8, thus breaking the motor circuit and bringing rheostat arm 8 to rest; but if`for any reason the contacts I4, I6 do not immediately separate, the rheostat arm 8 will eventually be brought to rest by contact with stop 8|, at which time the increased resistance to rotation will cause friction clutch Il, 64 to slip, and such slipping will continue until the motor circuit is interrupted.

Should the voltage rise above the normal value, the increased downward pull will tend to move contact I4h (on the under side of armature I4)v against the contact on insulated strip I1, and when these two come together the motor armature will receive current in the opposite direction,

wherefore rheostat arm 8 will move in a counterclockwise direction to insert more resistance in the shunt ileld circuit and correspondingly lower the voltage back toward normal; the circuit to the motornow passing from positive feed 8 by way of wire 8|, and contacts I1 and I4", to wires 4|, 8l and I4, and returning to the generator by wires I8, 82 and 58. Upon restoration of normal voltage the spring 8| will restore the armature I4 to its neutral (mid) position, thus deenergizing motor I3.

As the motor I8 need not be of any larger size' than is necessary to operate the arm 8 andthe reduction gear train (and slipping clutch) leading thereto, it can conveniently be mounted in a box-,like frame to be carried by the same mounting panel as that which receives the motor energizing magnet III, the relay Il, the rheostat Il. 'I8

`and the gear train of which the clutch elements 88, 84 form component parts. To this end I propose to mount, on one side |00 of such a boxlike frame, a pair of brush receiving strips and |02 (Fig. 2), and on the adjacent sides I mount the legs |88 and |08 (Fig. 1) of the field structure which receives the field winding III). The side is centrally apertured to receive a suitable bearing (not shown) to support one end of the motor armature assembly, and the opposite side is also apertured to allow passage therethrough of the shaft ||2 (Fig. l) which is driven from the motor armature. These box sides may be of any suitable material, and if of insulating material there will be a saving, as certain other insulating means may be dispensed with.

The adjusting means for spring 3| of the motor energizing magnet includes a sector |2| and a screw` |22 meshing therewith; the screw |22 being mounted in brackets |23 and |24 of the magnet assembly, and the sector |2| being pivotally mounted as indicated at |26. A post |21'is located on the sector |2| at a point which is spaced fromthe pivot |24, but substantially on the radial line passing from the pivot center to'the point of |21 serves 'as the anchorage ,for spring 3|, and because of its location on the radial line just referred to, it operates to vary the spring tension in response to every turn of screw |22; the teeth of sector |2| being held firmly in mesh with the screw |22 by the resilient action of the tooth- 4.

bearing portion vof the sector.

What is claimedis:

1. In combination witha generator and a rheostat for controlling theLvoltage-of the former, an electric motor energizable from said generator to vary the resistance setting of said rheostat, means for producing such energization whenever necessary to maintain constant voltage across the generator terminals, said energizing means comprising rtwo contacts leading to opposite sides of the generator circuit, and means for selectively connecting one or the other of 'said contacts in circuit with said motor to energize the latter with current from the generator circuit, said connecting means including an electro-magnet whose magnetic circuit is responsive to any deviation from normal -voltage across said 'generator terminals, and` an armature lin the magnetic circuit or said electro-magnet, said armature being a part of said motor circuit.

2. In combination with a generator and a rheostat for controlling the vo1tage`of` the former, an electric motor energizable from said generator to vary the resistance settingv of said rheostat, means for producing such energization whenever necessary to maintain constant voltage across the generator terminals, said energizing means comprising two contacts leading to opposite sides of the generator circuit, and means for selectively connecting one or current yfrom the generator circuit, said connecting means including anelectro-magnet whose magnetic circuit is responsive to any deviation from normal voltage across said generator terminals, an armature in the magnetic circuit of JOSEPH w. ALIEN.

the other of said contacts in circuit with said motor tolenergize the latter withl 

